However, these farm colonies, Kings Park State Hospital, (later named Kings Park Psychiatric Center) and Central Islip State Hospital (later named Central Islip Psychiatric Center), became overcrowded, like the institutions they were meant to replace.

The state bought approximately 1,000 acres (400 ha) of land in Brentwood and began construction on the hospital in 1929.

Pilgrim State Hospital opened on October 1, 1931, as a close-knit community with its own police and fire department, courts, post office, a LIRR station, power plant, swine farm, church, cemetery and water tower, as well as houses for staff and administrators.

Renowned filmmaker John Huston, who received a special commission in the U.S. Army Signal Corps during World War II, made a documentary at Mason General Hospital called Let There Be Light, which showed the effects of war on mental health.

As psychiatric medication and community care became an increasingly viable alternative to institutionalization, large mental institutions began to decline.

Edgewood, the last psychiatric hospital to be built on Long Island, closed its doors in December 1971, following decentralization.

In the early 1990s, with declining patient populations in the three remaining hospitals, the New York State Office of Mental Health (formerly the Department of Mental Hygiene) began making plans to re-organize the Long Island hospitals, which were implemented in the fall of 1996, when Kings Park and Central Islip were closed, and the remaining patients from those facilities were transferred to Pilgrim or released into community care.

Parts of Central Islip Psychiatric Center became a campus for the New York Institute of Technology, as well as a residential and commercial development.

A 52-acre (0.21 km2) portion of former parts of the Pilgrim campus has become the Brentwood State Park athletic field complex,[4] while the rest sits unused.

A former hospital building became Camusett Hall in 1972 and by opening day, half of Suffolk Community College was finished.

The former post office and vegetable garden property became Paumanok Hall in 1995 and old barns and other buildings became more education centers and classrooms by 1999.

Pilgrim State Hospital is mentioned in the 2009 documentary Cropsey, as having reportedly housed the mother of convicted child kidnapper Andre Rand.

The patient found with cuts on his head and bruises to his body; the aide arrested and charged with second-degree assault.

[11] Currently, Pilgrim Psychiatric Center is protected by members of the New York State Office of Mental Health Police.